Radiant steam heater construction and operation



Aug. 20, 1957 L. J. MARSHALL 2,303,227

RADIANT sTEAN HEATER CONSTRUCTION AND OPERATION Filed Nov. s, 1953 2 sheets-sheet 1 lobi) `l /12 33, 37, 3a

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Aug. 20, '1957 L. J.- MARSHALL RADIANT STEAM HEATER CONSTRUCTION AND OPERATION Filed NOV. 3, 1953 2 Sheets-Sheet 2 @n mm\ F. Q) N\ f L w VN MN r I l v bv mw QM l# o mm n hm. MN Mm mm QN N 7 E v t\ @SEQ 32mb N Lmmubuohw INI/ENTOR.

Leonard J. Marshall TTORNEY United States Patent O i RADIANT STEAM HEATER CONSTRUCTION AND OPERATION Leonard J. Marshall, Tenafly, N. J., assigner to Combustion Engineering, Inc., New York, N. Y., a corporation of Delaware Application November 3, 1953, Serial No. 389,959 9 claims. `(ci. 122-473) This invention relates to steam heaters such as superheaters and reheaters and is particularly applicable to the radiant type in which the heat absorbing surfaces are directly exposed to the radiant heat of the products of combustion within a furnace.

Large steam generating units providing steam for steam turbines such as are used in large public utility plants are required to furnish higher steam temperatures for both the initial superheated steam to the turbine and the steam to be reheated from one or possibly more interstages of the turbine. To provide for these high temperatures consideration must be given to the use of other than the conventional convection type of superheaters and reheaters and such steam heaters as the radiant and the platen types have been used to obtain higher temperatures.

The radiant type of superheaters and reheaters have been applied to furnace walls, the steam heater tubes being arranged in a similar manner to the usual closely spaced tubes of water walls. Such steam heater tubes have been subject to transverse cracking due to temperature differences existing between the side of the tube facing the furnace and the opposite side facing the wall, the temperature difference being caused by the high rate of vheat absorption of the tubes on the furnace side compared with practically no absorption on the opposite side.

Platen types of superheaters or steam heaters have been located close to the furnace oiftake to be contacted bythe products of combustion leaving the furnace and comprise rows of aligned tubes spaced about two to four feet apart, each row being generally parallel to the flow of the products of combustion thereover. They are generally hung from above and are limited in length for the purpose of providing proper rsupport and avoidance of warping. Arranged in this manner, the amount of heat absorbed by radiation is relatively low. Platens of this type increase the superheater cost because of the large surface required.

To overcome the above objections incurred by the wall type radiant and the platen type superheaters, long vertical platens have been proposed extending over a large portion of the height of a vertical furnace. An objection to this construction is the warping of the superheater tubes which occurs when they are subject to high heat absorption rates and high temperatures. With such construction there is no satisfactory means of supporting the tubes to maintain their alignment except at their ends.

It is an object of this invention to overcome the above mentioned objections by providing a novel arrangement of relatively short, spaced parallel rows of aligned superheater tubes extending across the furnace several times in combination with arches projecting into the furnace from walls thereof through which arches the tubes pass and where they are supported to maintain their alignment.

Additional objects and advantages will become Vapparent from the following description of an illustrative embodiment of the invention when read in conjunction with the accompanying drawings wherein:

Fig. 1 is a crossl section in elevation through the fur- 2 nace of a large steam generating unit embodying one form of the invention taken on line 1 1 of Fig. 2.

Fig. 2 is a plan View of Fig 1 taken on line 2-2 of Fig. 1, and shows two similar side by side furnaces, one of which may contain a superheater and the other a reheater. Both of these furnaces utilize the invention.

Figs. 3 and 4 are cross sections taken through the irnproved superheater, taken respectively on lines 3 3, 4--4 of Fig. 1.

Fig. 5 is a diagrammatic representation similar to Fig. 1, of another application of the invention.

Referring to Fig. 1, a typical steam generating unit comprises a furnace 1 whose front, rear, side walls and roof 2, 3, 4 and 5 respectively may be faced with steam generating tubes 6, 7, 8 and 9. These steam generating tubes discharge their steam-water mixtures into a steam and water separating drum 10 via headers 11 and pipes 12 and receive water from drum 10 via downcomer 13, bottom distribution drum 14, supply pipes 15 and headers 16. Downcomer 13 may be connected through a circulation pump 17 as shown or the pump may be omitted and the upper and lower portions of downcomer 13 may be interconnected via the by-pass 13a.

`Fuel and air for combustion are delivered into furnace 1 through burners 18 which discharge a fuel and air stream vertically downward in an offset portion la'of the furnace 1 through an arch 19. The products of combustion generally follow the path of a ligure U and rise within the furnace 1 to leave through an offtake 20. In flowing through the oiftake 20 the products may ilow over convection steam heating surface 21 which may be a reheater or a section of the superheater. Upon leaving the offtake 29 the products may flow downwardly through a conduit 22 within which may be other heat absorbing surface such as further superheating or reheating surface or economizer surface 23 for heating feed water.

The furnace 1 is provided with arches 24 and 25 extending into the furnace from the front and rear walls 2 and 3 the inside faces of which arches may be lined with some or all of the steam generating tubes 6 and 7 facing these walls. There are two such arches shown although others may be used extending into the furnace from opposite side walls. The lower face of arch 24 is substantially a continuation of the arch 19 or the tubes facing the arch, through which the burners 18 direct the fuel into the furnace 1. Arch 25 is located in the side forming the bottom 26 of the oftake 21) and its upper face is substantially a continuation of the bottom 26 of otftake 20.

Steam heating tubes 27 pass across the furnace 1 between opposite walls 3 and 2 and the roof 9. These tubes extend continuously between headers 28 located adjacent one wall 23 and headers 29 located adjacent the roof 5 just above the entrance to oiftake 20. The steam heating tubes 27 are arranged in spaced rows 30 of tubes (see Figs. 3 and 4), the tubes 27 of each row 30 being aligned in direction generally parallel to the flow of the products of combustion through the furnace 1. All of the rows 30 pass through arches 24 and 25 and are sup ported for alignment at each arch as shown in Fig. 4. Figs. 1 and 4 show steam generating tubes 6 along front Wall 2 being bent inwardly of the furnace 1 to form or to face the nose of arch 24. A pair of tubes 6 is positioned closely adjacent each of therows 30 of steam heating tubes on both sides thereof to provide lateral support for tubes 27. In this manner each row of tubes 27 is maintained in alignment when passing through the arch. By providing an appropriate number of arches, the unsupported length of the steam heating tubes 27 may ac cordingly be kept Within allowable limits. Obviously, if desired, the rows 30 of tubes 27 may be anchored within each arch. Fig. 4 shows by way of example, six

steam generating wall tubes 6 between adjacent rows 30 of steam heating tubes 27.

Preferably fluid cooled or steam generating tubes 31 are provided as end tubes for each row 30 of steam heating tubes 27 so as to protect the adjacent steam heating tubes 27 from excessive uneven exposure to heat. These protecting end tubes 31 lie adjacent the bottom of the steam heating tubes 27 preferably throughout the latters extent within the furnace 1 and adjacent the top of the tubes 27 of the bottom row 30. These protecting tubes 31 are connected into the circulation of the steam generator through extensions 32 of the bottom water wall headers 16 via tubes 32a and through the top water wall headers 11 and tubes 12.

The top and bottom headers 29 and 28 are preferably anchored and expansion of the steam heating tubes 27 is cared for by the spring in the tubes which are, as here shown (in Fig. 4) free to move in the arch 24. Means are preferably provided to seal the space between the rows 30 of tubes 27 and the structure of arch 25 so as to prevent the ow of the products of combustion through the arch.

Fig. 2 shows a plan view of two adjacent furnaces 1 and 1b comprising a unit, one of which may contain a superheater and the other a reheater, both embodying the invention. The section 1-1 applies to either one of the furnaces and the end connections of the steam heating tubes will be similar so that the description of the connections for one of the furnaces will also serve for the other, Steam from steam drum (or from a reheater inlet header 10b connected to an interstage of a steam turbine not shown) flows respectively via pipe 33 or 33b into top header 29 or 29b of the end row of steam heating tubes 27. From said header 29 the steam ows downwardly through said end row of tubes 27 to the bottom header 28 (Figs. 1, 2) thence to the next adjacent bottorn header 28 via pipe 34, thence upwardly through the tubes 27 of the second row 30 into the associated top header 29 and thence through pipe 35 into the outlet header 36 or 36b respectively (Figs. 1, 2). steam ows from drum 10 (or header 10b) through pipes 37, 38 (or 3812) respectively into the associated top headers 29 thence down the row 30 of tubes 27 connected to said top headers 29, and into bottom headers 28,A thence through connections 39, into the adjacent bottom headers 28 thence up through the rows 30 of tubes 27 connected thereto into the associated top headers 29 and thence via tubes 40, 41 into the outlet header 36 (or 36b) respectively. Obviously the steam may be caused to optionally ow downwardly or upwardly in parallel streams through all of the rows 30 of steam heating tubes 27 instead of as described above.

Fig. 5 is a diagrammatic representation of the furnace 1 shown in Fig. 1 except that the offset 1a is omitted and the burners 18 are disposed to project the fuel stream transversely through a vertical wall 2 of the furnace or through all of the vertical walls 2, 3, 4 adjacent the corners thereof so as to provide a vortical ame within thefurnace. In this disclosure the rows 30 of steam heating tubes 27 cross the furnace 1 but once, the crossing of the oiftake opening being similar to that shown in Fig. 1. There is but one arch extending into the furnace 1 at the bottom of the offtake 20.

By my novel arrangement of the radiant superheater within the furnace substantially all of the surface of the superheater tubes around the circumference is effective in absorbing heat which materially reduces the length of the tubes or the amount of surface required when compared with the radiant-superheater having its tubes on the furnace walls.' This results in a relatively lower steam pressure drop thru the superheater. Furthermore the cost of alloy tubing required by such a superheater is low when compared with the amount of such tubing required in a radiant superheater having its tubes facing the furnace walls.'V By the presence Vof my novel -super- Similarly heater within the furnace, the total effective heat absorbing surface of the furnace is relatively increased and consequently a relatively smaller furnace may be used to cool the products of combustion leaving the furnace to a desired temperature.

Furthermore, arches 24, 25 (either one or more) are made use of in laterally supporting rows of steam heating tubes thereby acting as intermediate anchors or guides. This will permit the use of longer continuous tubes fully exposed to the furnace heat without the danger of warping and vibration.

While I have here shown and described two embodiments of my invention it will be understood that changes in construction, combination and arrangement of parts may be made without departing from the spirit and scope of the invention as claimed.

I claim:

1. In a vapor generating and heating unit, an elongated furnace bounded by walls and having a gas offtake in one end portion thereof, fuel burning means associated with said furnace and remote from said olftake with respect to gas flow, vertical tubes forming at least one arch projecting into the furnace from a` wall thereof and at a location intermediate said oiftake and said fuel burning means, rows of continuous superheating tubes extending longitudinally through the furnace and in spaced relationship with the walls and with each other, said continuous superheating tubes passing through the projecting portion of said arch; and a pair of said arch forming tubes positioned closely adjacent at each side of said superheating tubes in laterally supporting relationship with said superheating tubes, whereby said arch provides an intermediate sliding support for said rows of superheating tubes preventing excessive warping and vibration thereof.

2. In a steam generating and heating unit, an upright furnace bounded by Walls including a front wall, a rear wall, opposing side walls, and a roof, said furnace having a gas oiftake in the upper portion of said rear wall; fuel burning means associated with said furnace and remote from said oltake with respect to gas flow; vertical tubes forming an arch projecting into the furnace from said rear wall and at a location adjacent and below said offtake; and rows of continuous steam heating tubes closely spaced in direction of gas flow and extending from said front wall across the furnace said rows being spacedly aligned with said opposing side walls and with each other, said continuous steam heating tubes being supported by said front wall at one end thereof and passing through the furnace portion below said arch, through the projecting portion of said arch, and continuing upwardly across said offtake to said furnace roof; and a pair of said arch forming tubes positioned closely adjacent at each side of said superheating tubes in laterally supporting relationship with said superheating tubes,

whereby said arch provides an intermediate sliding support for said rows of continuous steam heating tubes preventing excessive warping and vibration thereof.

3. A furnace and steam heater combination as claimed in claim 2 further characterized by steam generating tubes arranged parallel to and forming end tubes of said rows in direction of gas flow thereby protecting the next adjacent steam heating tubes from excessive heat liberated by the products of combustion.

4. In a steam generating unit, a furnace bounded by side walls and having an olftake in one side wall, fuel burning means associated with said furnace remote from said offtake with respect to the flow of products of combustion therethrough, steam heating tubes exposed to the products of combustion of said fuel within said furnace, vertical tubes forming at least one arch projecting into said furnace between said offtake and said fuel burning means from at least one of opposite walls, said steam heating tubes extending continuously from a point of entrance into said furnace located remote from said oltake in one of said opposite side walls to a point of exit located adjacent and above said oltake, said tubes extending at least once across the furnace between said opposite side walls, through said arch and upwardly across said oiftake into said point of exit from the furnace, said steam heating tubes being arranged in spaced rows the tubes of each row being aligned in direction generally parallel to the ow of the products of combustion through the furnace; a pair of said arch forming tubes positioned closely adjacent at each side of said steam heating tubes in laterally supporting relationship with said steam heating tubes whereby said arch provides an intermediate sliding support for said rows of steam heating tubes preventing excessive warping and vibration thereof.

5. A furnace and steam heater combination as claimed in claim 4 further characterized by steam generating tubes arranged parallel to and forming end tubes of said rows thereby protecting the next adjacent steam heating tubes from excessive heat liberated by the products of combustion.

6. In a steam genera-ting and heating unit, an upright furnace bounded by walls including a front wall, a rear wall, opposing side walls, and a roof, said furnace having a gas offtake in the upper portion of said rear wall; fuel burning means associated with said furnace and remote from said offtake with respect to gas flow; vertical tubes forming an upper arch projecting into the funrace from said rear wall and at a location adjacent and below said oiftake; vertical tubes forming a lower arch projecting into the furnace from said front wall at a substantially lower elevation than said upper arch; and rows of steam heating tubes extending from a point in said rear wall below said lower arch elevation across the furnace to said front wall in spaced relationship with said opposing side walls and with each other, said steam heating tubes passing through the furnace portion below said lower arch, through the projecting portion of said lower arch, continuing across said furnace to said upper arch, passing through the projecting portion of said upper arch, and continuing upwardly across said offtake to said furnace roof; and a pair of said lower arch forming tubes and a pair of said upper arch forming tubes each positioned closely adjacent at each side of said steam heating tubes in laterally supporting relationship with said steam heating tubes, whereby said upper and lower arches provide intermediate sliding supports for said rows of steam heating tubes preventing excessive warping and vibration thereof.

7. A furnace and steam heater combination as claimed in claim 6 having in addition steam generating tubes arranged parallel to and forming end tubes of said rows thereby protecting the next adjacent steam heating tubes from excessive heat from the products of combustion.

8. In a vapor generating unit a relatively long and narrow vertical furnace bounded by side walls and a roof and having an oltake in one side wall adjacent the roof; burners projecting a stream of fuel into the furnace remote from the oiftake, the products of combustion of said fuel following a path through the furnace towards said oftake; vertical tubes forming vapor cooled arches projecting into said furnace from opposite side walls between said oitake and said burners, one of said arches being located in the wall beneath said oftake and forming the bottom of said oiftake and another of said arches being located above and adjacent said burners; vapor heating tubes extending in rows continuously between one group of headers located remote from said oiftake adjacent one of said opposite side walls and another group of headers adjacent said roof above said offtake, said tubes passing through the projecting portion of all of said arches, and extending from one group of headers to the other at least once across the furnace between said opposite side walls into said olftake arch and across said olftake, said vapor heating tubes being arranged in spaced rows the tubes of each row being aligned in direction generally parallel to the ow of the products of combustion through the furnace; and a pair of each of said tubes forming said arches positioned closely adjacent at each side of said vapor heating tubes in laterally supporting relationship with said vapor heating tubes, whereby said arches provide intermediate sliding means of support for said rows of vapor heating tubes preventing excessive warping and vibration thereof.

9. In a steam generating unit a relatively long and narrow vertical furnace bounded by side Walls and a roof and having an olftake in one side wall adjacent the roof; burners projecting a stream of fuel vertically downwardly into the furnace thru the roof of an offset in the lower portion of one side wall, the products of combustion of said fuel rising upwardly through the furnace to said offtake; vertical tubes forming steam cooled arches projecting into said furnace from opposite side walls between said offtake and said burners, one of said arches being located in said oitake containing wall and forming a continuation of the bottom of said ofitake and another of said arches forming a continuation of said ofsets roof adjacent said burners; steam heating tubes extending in rows continuously between one group of headers located remote from said offtake adjacent one of said opposite side walls and another group of headers adjacent said roof above said otftake, said tubes passing through the projecting portion of all of said arches, and extending from one group of headers to the other at least once across the furnace between said opposite side walls into said oitake arch and across said offtake, and being arranged in spaced rows the tubes of each row being aligned in direction generally parallel to the ow of the products of combustion through the furnace; and a pair of each of said tubes forming said arches positioned closely adjacent at each side of said steam heating tubes in laterally supporting relationship with said steam heating tubes, whereby said arches provide intermediate sliding means of support for said rows of steam heating tubes preventing excessive warping and vibration thereof.

References Cited in the tile of this patent UNITED STATES PATENTS 1,927,892 Jones Sept. 26, 1933 2,308,762 Krug et al Ian. 19, 1943 2,357,300 Bailey Sept. 5, 1944 FOREIGN PATENTS 1,045,900 France luly l, 1953 

